A013951 Start with 1, apply 1->12, 21->21, 22->21, 2->2 (for final 2); take limit; note positions of 1's.

1, 4, 5, 7, 10, 12, 13, 16, 17, 20, 21, 23, 26, 27, 29, 32, 34, 35, 37, 40, 42, 43, 46, 47, 50, 52, 53, 56, 57, 60, 61, 63, 66, 67, 70, 71, 74, 75, 77, 80, 81, 83, 86, 89, 91, 94, 95, 97, 100, 101, 103, 106, 108, 109, 111, 114, 116, 117, 120